1. Field of the Invention
The disclosed technology relates to the field of optical measurements for determining an active dopant profile, and more particularly, to an optical measurement method and system for determining the peak concentration and junction depth of an active dopant profile.
2. Description of the Related Technology
The electrical characterization of the source and drain extension regions of CMOS transistors is highlighted in the ITRS roadmap for semiconductors as a major challenge for future technology nodes. In practice, there is a clear need for techniques which are simultaneously accurate, non-destructive, fast, local and highly reproducible. The photomodulated optical reflectance (PMOR) technique has shown to be a very promising candidate to solve this need.
The photomodulated optical reflectance (PMOR) is a fast, non-contact technique. It has shown very promising to solve the need for non-destructive carrier profiling tool for ultra-shallow junctions (USJs). This pump-probe technique is based on the measurement by a probe laser of the reflectance change due to the modulated pump laser-induced changes in refractive index. The theoretical basis of the technique has been widely studied on metals, homogeneous semiconducting materials and as-implanted (i.e. damaged) silicon samples. The existing theories are all based on simplified optical and transport models, where a certain number of effects are neglected without any justification. Typically, the optical model is based on the Drude electrorefractive effect and the thermorefractive effect. As for the transport models, they usually only consider diffusion and recombination effects. This assumes that, apart from thermal carrier generation and recombination heat, no coupling exists between the carrier and heat transport equations.
Thus, although the PMOR technique has been widely studied on homogeneous bulk material and on as-implanted (i.e. unannealed) doping profiles, the extension towards active doping profiles allows for further improved methods and systems for determining active dopant profiles.